With the increase in meningeal leukemia and the interest in neoplasms within the central nervous system, the use of intrathecal chemotherapy is expected to continue to increase. In this ongoing project, a relatively standardized technique for evaluating intrathecal chemotherapy in monkeys is being employed and provides a resource for rapid evaluation of any concepts and ideas as they develop. The project is being used to test a specific agent of choice, rather than to generally screen chemotherapeutic drugs; therefore, this research operates on a demand basis. Intracisternal installation of carefully chosen drugs are first performed to determine acute immediate toxicity. From this information, dose levels for chronic studies simulating the dose schedules used in man are developed. Previously, the use of intrathecal Ara-C was defined in this project, and more recently, the data necessary for the use of intrathecal thiotepa has been developed. The Phase I Study in man authenticated the findings in monkey. The project has been in a holding pattern during the course of this year, however, we will undertake the evaluation of an additional chemotherapeutic agent in the forthcoming year.